1. Field of the Invention
This invention relates to a controlled-deflection type of roll used to process traveling webs, such as paper in a papermaking machine. More particularly, this invention relates to a controlled deflection roll which operates at elevated temperatures to heat the web. Even more particularly, this invention relates to a barrier within such a controlled-deflection roll which separates the extremely hot hydraulic fluid used to actuate the roll shell deflection apparatus, and the heat of the hydraulic fluid, from the bearing lubricant. Still more particularly, this invention relates to a barrier having one or more fluid chambers which contain a cooling liquid which is separate from either the internal hydraulic fluid or the bearing lubricant and which establishes a heat barrier between the internal hydraulic fluid and the bearing lubricant.
2. Description of the Prior Art
As controlled-deflection rolls have developed, and as papermaking has evolved into a more efficient hot-press water removal technology, the operating temperatures of controlled-deflection rolls have increased, particularly in the press section of a papermaking machine to remove moisture, and in the calender section to improve sheet properties. In early designs of controlled deflection rolls, the same oil was often used to both lubricate the bearings and the interface between the shoe, or shoes, which move against and support the roll shell to modify its deflection to maintain the profile of the roll shell along its nip line of contact with a mating roll in a desired contour. The operating temperatures were not excessively high because nip pressures were generally lower, rolls were generally shorter in length, speeds were lower, and the rolls in the press and calender sections in a papermaking machine were not run hot. Often, more than one of these factors was present.
as nip pressures and machine speeds increased, and as papermaking machines became wider, and with the advent of so-called hot pressing wherein the press section of the papermaking machine is desired to run hotter in order to enhance the removal of as much moisture from the traveling paper web as far upstream in the papermaking process as possible, the operating temperature of the hydraulic actuating fluid within controlled-deflection rolls increased to a level beyond that at which the roll shell support bearings, and their lubricant, could operate at the load levels and service life required of them. Similarly, modern calendering techniques also utilize higher roll temperatures. Even if special high temperature bearing lubricant was used, its exposure to either the thinner, less viscous hydraulic fluid used to actuate the deflection correcting apparatus and lubricate its interface with the roll shell, or to the temperature of the hydraulic fluid, or both, was deleterious to the lubrication of the bearings and to their service life. Further, merely sealing the roll shell support bearings from physical contact with the internal hydraulic fluid does not insulate the bearings from the deleterious effects of the increased heat of the hydraulic fluid.
In some prior lubrication arrangements in controlled-deflection types of rolls, the bearings were lubricated with oil which, in turn, was directed into the roll where it either was used to actuate the roll shell support shoe, or mixed with such oil before they were recirculated out of the roll. While such an arrangement operates satisfactorily, it either requires the same lubricant to be used to lubricate the bearings and to actuate the shoe apparatus to control the roll shell deflection, or, if separate lubricants are used, they must necessarily be mixed within the roll and become undesirable for recirculation and subsequent use in either of these functions.